Because mathematicians love giving simple things ridiculously grand names. Vertex comes from Latin, meaning “whirl” or “summit,” which is just a posh way of saying “pointy bit.” It’s like calling your living room a “residential spatial unit.”
But here’s the kicker: the plural isn’t “vertexes,” unless you want your geometry teacher to cry into their coffee. It’s vertices. Yes, with an “ices” like “vortices” or “alumni.” It’s the kind of word that makes you feel smarter just by trying to pronounce it. “I have two vertices, and they’re both sharp.”
